As you can see, there's a pretty wide range in the few responses you've already gotten. Pay close attention to Diver0001's post. It's not about numbers. It's about you and your gear. There are still times I do a solo dive now when I think about the what ifs and how I would handle it alone. If you never think about those things, or you begin solo diving and stop thinking about those things, then you shouldn't be solo diving. It's not about confidence as much as it's about respect - respect for the fact that we are humans placing ourselves into an environment that is not natural for us and things can happen to really accentuate that.